One of the most efficient methods for making a large display is to use projected images. Conventionally, the most advanced projection systems use imaging devices such as digital micro-mirror (DMD), Liquid Crystal on Silicon (LCoS), or transmissive LCD micro-displays. Typically, one or two fold mirrors are used in projection displays in order to fold the optical path and reorient it to reduce the cabinet depth of projection displays. In a single fold mirror rear projection display, the light engine converts digital images to optical images with one or more microdisplays, and then projects the optical image to a large mirror which relays the optical images through a rear projection screen to a viewer in front of the screen. The light engine also manages light colors to yield full color images and magnifies the image. In a two fold mirror rear projection display, the projected optical images from the light engine are reflected off of a first fold mirror to a second fold mirror, and then through the rear projection screen to a viewer. The two fold mirror structure provides additional reduction in TV cabinet depth over one fold mirror structures, but typically requires additional cabinet height below the screen. The height of the cabinet below the screen is called chin height and it grows as the light engine projects to a first fold mirror typically positioned below the screen.
Because the imaging devices in projection displays are small, typically less than 1″ in diagonal, they are inexpensive to manufacture. However, the small images generated by the imaging devices require magnification factors up to 100 in order to yield the 50″-80″ diagonal image typical in consumer projection televisions. However, the large amount of magnification can cause large alignment issues from just a small miscalibration or error in the position of the light engine or mirrors.
Rear projection televisions (RPTVs) made today typically have separate mechanical assemblies for the projector (known as a light engine), the structures that hold the mirrors, and the surrounding enclosure. This is introduces the following problems:                The light engine lens must be designed to match the throw distance of the cabinet's optical assembly. However, since light engines are designed and built separately from the rest of the system, this “lens matching” problem often delays the completion of the light engine design.        The light engine, mirror and screen positions in the cabinet determine the overall angle that the projected light hits the back of the screen. These angles are required to begin the design of the screen Fresnel lens. Since the relative positions of the engine, mirrors and screen are determined after the engine is designed and selected, the tooling of the Fresnel lens and the integration of the product cannot be completed until late in the project. This results in an increased overall project length, and delays product time to market.        Once the light engine is installed in the cabinet the alignment of the picture on the screen is not guaranteed. Various adjustments need to be made in the optical path to correctly size and position the image, often resulting in excessive manufacturing cycle time.        Light engines are complex optical systems and are typically built by specially trained technicians in a clean room environment. The remaining optical path is typically built by minimally trained workers in a traditional TV production line environment.        However, the complex optical adjustments are made at this second stage of manufacturing. The results are not good: dirt and dust are introduced into the optical system and the system is difficult to align correctly.        During shipping of the calibrated system from the factory to the dealer or customer, various parts of this patchwork optical assembly can shift position causing the image to become misaligned.        
As such, a new optical assembly and method are needed to overcome the above-mentioned disadvantages.